1. Field of the Invention
This invention relates to a method and technology of a hybrid stacked flip chip for a solar cell and, particularly, to that of manufacturing a simple and higher efficient solar cell.
2. Description of Related Art
As shown in FIG. 4A, the solar cell comprises a substrate 60 of silicon (Si), germanium (Ge), or Si/Ge. On the substrate 60, a P-N junction semiconductor layer 61, such as Si/SiGe, that may absorb a long wavelength (e.g. infrared rays), is formed. It has an efficiency of around only 15%.
A compound solar cell is formed by a compound semiconductor on a substrate to absorb a medium wavelength solar spectrum. Owing to a direct bandgap, it has higher efficiency and absorbs the correspondent wavelength of around 25%. As shown in FIG. 4B, the solar cell comprises a substrate 70 of GaAs, AlGaAs, InGaP or GaP. On the substrate 70, a P-N junction semiconductor layer 71, such as GaAs/AlGaAs, GaAs/InGaP, GaP/GaP, GaAs/AlInGaP, and GaAs/AlGaAs, etc., that may absorb a medium wavelength (e.g. visible rays), is formed.
As shown in FIG. 4C, the solar cell comprises a substrate 80 of Al2O3 sapphire, silicon carbide, or ZnO. On the substrate 80, a P-N junction semiconductor layer 81, such as GaN/AlGaN, GaN/InGaN and InGaN/AlGaN that may absorb a short wavelength (e.g. ultraviolet rays), is formed.
However, each solar cell mentioned above may absorb only the correspondent long wavelength (as shown in FIG. 4A), medium wavelength (as shown in FIG. 4B), or the short wavelength (as shown in FIG. 4C), respectively.
Thus, recently, a tandem cell is provided in which materials of different bandgaps are stacked into the cell of multiple junctions.
As shown in FIG. 5A, the solar cell comprises a substrate 60 of Si, Ge, or Si/Ge. On the substrate 60, a P-N junction semiconductor layer 61, such as Si and SiGe, that may absorb the long wavelength is stacked so as to absorb rays of light, and an tunnel junction 10 is formed on the P-N junction semiconductor layer 61. On the tunnel junction 10, a P-N junction semiconductor layer 71, such as GaAs, that may absorb the medium wavelength, is then stacked, and the tunnel junction 10 is formed on the P-N junction semiconductor layer 71. On the tunnel junction 10, a P-N junction semiconductor layer 72, such as AlGaAs or InGaP, which may absorb the medium wavelength, is then stacked.
As shown in FIG. 5B, the solar cell comprises a substrate 70 of GaAs, As, or GaP. On the substrate 70, a P-N junction semiconductor layer 71, such as GaAs, that may absorb the medium wavelength, is then stacked, and the tunnel junction 10 is formed on the P-N junction semiconductor layer 71. On the tunnel junction 10, a P-N junction semiconductor layer 72, such as AlGaAs or InGaP, which may absorb the medium wavelength, is then stacked.
However, Si/SiGe, GaN/AlGaN, and GaAs/AlGaAs used for the semiconductors are quite different, so the semiconductor epitaxy when formed is easily polluted with each other, and lattice matching is also very different.
Typical tandem solar cell is comprised of a p-type semiconductor connected to an n-type semiconductor, and a parallel p-type semiconductor connected to an n-type semiconductor and has two terminals. Total voltage is a sum of V1 and V2. Current of the typical solar cell is no greater than Imin. Power P is a sum of (V1+V2)*Imin.
Consequently, because of the technical defects of described above, the present invention was developed, which can effectively improve the defects described above.